The phrase “population crisis” once roused fears of uncontrollable growth in human numbers. However, now that many societies have improved women's status and increased access to family planning, some analysts argue that if there is a population crisis it is because women are having too few children-a so-called “birth dearth.” A quick look at the demographic reality shows that the era of population growth is far from over-and high fertility rates are still prevalent in many developing countries.

The Millennium Development Goals (MDGs) offer precise targets for reducing poverty and promoting global development, but they remain incomplete if they do not build from and incorporate the objectives of other major international agreements, particularly those reached at the International Conference on Population and Development (ICPD) and the Fourth World Conference on Women (Beijing). At the 2005 World Summit and in the years leading to the 2015 milestone, the sexual and reproductive health community is taking every opportunity to advance this message: universal access to sexual and reproductive health services is essential to achieving the MDGs.

During the last three decades of the 20th century, demographic transition - a population's shift from high to low rates of birth and death - was associated with continuous declines in the vulnerability of countries to civil conflicts (ethnic wars, antigovernment insurgencies and terrorism resulting in multiple deaths). This relationship suggests that a range of policies and programs that promote demographic transition by encouraging small, healthy and better educated families and longer lives will improve the prospects for political stability in developing countries and enhance global security in the future.

More than 850 million people worldwide are classified as undernourished, many of whom suffer from chronic hunger (also known as food insecurity). Rapid population growth is intensifying food insecurity in parts of the developing world, particularly in sub-Saharan Africa where some countries' populations are doubling and tripling every 30-50 years. Greater investments in voluntary family planning programs and supplies, including contraceptives, are urgently required to meet the needs of more than 200 million women worldwide who wish to delay or end their childbearing but do not have access to modern and effective contraceptive methods.

Reproductive illnesses and unintended pregnancies undermine economic development by weakening and killing adults in the prime of their working lives, by disrupting and cutting short the lives of their children, and by placing heavy financial and social burdens on families. In most developing-country settings, much of the loss of life and human productivity that is due to poor reproductive health could be prevented with affordable and cost-effective programs.

Economists credit declining fertility, from the mid-1960s to the early 1990s, as a major contributor to sustained economic growth among the Asian Tigers - the economically vibrant nations of South Korea, Taiwan, Thailand, Singapore, Indonesia, Malaysia and the former Hong Kong Territory. Research indicates that shifts to smaller family sizes and slower rates of population growth played a key role in the creation of an educated workforce, the accumulation of household and government savings, the rise in wages, and the impressive growth of investments in manufacturing technology.

Continued high rates of AIDS-related illness and death in some of the world's poorest countries could impose unprecedented changes in their population age structures, stunt their economic development and retard their demographic transition – the change from a population characterized by short lives and large families, to one with long lives and small families. These impacts promise to leave the most seriously AIDS-affected countries even more vulnerable to political instability and civil conflict. How the world responds to the HIV/AIDS pandemic in this decade could bear heavily upon the future of global security.

The world's population more than doubled in the last half-century and still is increasing. Absent an unexpected dramatic shift in family size or catastrophic increases in death rates, it could add 2.5 billion people before peaking. Worldwide, the largest group of young people ever is entering their reproductive years, requiring an expansion of family planning services to enable more couples to have the smaller families and later pregnancies they desire. In the long term, this will contribute to individual and family well-being, a slowdown in population growth and sustainable economic development.

Population age structure-the comparative size of specific age groups relative to the population as a whole-can help illustrate where countries' risks and opportunities lie in relation to critical issues such as democracy, development and security. In fact, the influence of age structure on a state's governance, risk of an outbreak of civil conflict, and economic development is both significant and quantifiable. Given these linkages, investments in family planning, infant and maternal health, education and economic opportunities for girls, women and young people can vastly affect the shape of things to come.

In 1994, at the International Conference on Population and Development (ICPD), 179 nations agreed on a plan for achieving universal access to basic reproductive health care by 2015. Today, vast differences remain in reproductive health status between rich and poor countries. The HIV/AIDS pandemic exacts a growing toll in human lives and threatens economic growth in some of the world's poorest countries. Donors focused on achieving the Millennium Development Goals – and concerned with poverty reduction, human rights, health and development – must help ensure the adequate flow of financial resources (referred to as population assistance) for sexual and reproductive health services.